I don't claim to be a genius player, and after 10 attempts, I still couldn't complete the 3rd mission in the Inferno campaign!!!!! It's terrible! This elf keeps defeating me, the upper city is guarded by him, the dragons destroy my troops, I have little money, and my growth is slow! Oh! What should I do? Please advise! :-)
1. Rush, as already mentioned. In general, this is the most correct way, but if it doesn't work, you can try...
2. A long and exhausting strategy against the AI. We wait for 1 week, buy everything we can in our city, quickly capture the first elven city and start building it (it's better to build Ents right away). We wait and accumulate strength. Then, a hero with superior forces will attack us. We surrender the city without a fight and go to another elven city. Everything will already be built there, we buy everything there. They will come after us again, and we surrender the city again and go to the third. And so on in a circle. The AI will divide its army into parts, and sooner or later, we will defeat first one half of its troops and then the other. And AS QUICKLY AS POSSIBLE, KILL THE DRUIDS! They create neutral creatures on the map that join the AI's army.
I was just completing it using the second method, but it's long and tedious, and it requires experience. Moreover, it's so long that I received 72k experience for the final battle. If there wasn't a limit....
P.S. I wonder what difficulty level everyone completed this mission on? I played on Veteran.